The present disclosure relates to fluids, additives, and methods for use in subterranean treatments, and more specifically, to dual-purpose additives that may be used as viscosifying agents and surface active agents in fluids, subterranean treatments, and oilfield operations.
Viscosified treatment fluids may be used in a variety of subterranean treatments and oilfield operations. As used herein, the term “treatment,” or “treating,” refers to any subterranean operation that uses a fluid in conjunction with a desired function and/or for a desired purpose. The term “treatment,” or “treating,” does not imply any particular action by the fluid. Examples of common subterranean treatments include, but are not limited to, drilling operations, pre-pad treatments, fracturing operations, perforation operations, preflush treatments, afterflush treatments, sand control treatments (e.g., gravel packing), acidizing treatments (e.g., matrix acidizing or fracture acidizing), diverting treatments, cementing treatments, and well bore clean-out treatments. For example, in certain fracturing treatments generally a treatment fluid (e.g., a fracturing fluid or a “pad fluid”) is introduced into a well bore that penetrates a subterranean formation at a sufficient hydraulic pressure to create or enhance one or more pathways, or “fractures,” in the subterranean formation. These cracks generally increase the permeability of that portion of the formation. The fluid may comprise particulates, often referred to as “proppant particulates,” that are deposited in the resultant fractures. The proppant particulates are thought to help prevent the fractures from fully closing upon the release of the hydraulic pressure, forming conductive channels through which fluids may flow to a well bore penetrating the formation. Treatment fluids may also be used in a variety of pipeline treatments, either in subterranean pipelines or pipelines above ground.
Maintaining sufficient viscosity in treatment fluids may be important for a number of reasons. Viscosity is desirable in drilling operations since treatment fluids with higher viscosity can, among other things, transport solids, such as drill cuttings, more readily. Maintaining sufficient viscosity is important in fracturing treatments for particulate transport, as well as to create or enhance fracture width. Particulate transport is also important in sand control treatments, such as gravel packing. Maintaining sufficient viscosity may be important to control and/or reduce leak-off into the formation, improve the ability to divert another fluid in the formation, and/or reduce pumping requirements by reducing friction in the well bore. At the same time, while maintaining sufficient viscosity of a treatment fluid often is desirable, it also may be desirable to maintain the viscosity of the treatment fluid in such a way that the viscosity may be reduced at a particular time, inter alia, for subsequent recovery of the fluid from the formation. To provide the desired viscosity, polymeric viscosifying agents commonly are added to the treatment fluids. The term “viscosifying agent” is defined herein to include any substance that is capable of increasing the viscosity of a fluid, for example, by forming a gel. Examples of commonly used polymeric viscosifying agents include, but are not limited to guar gums and derivatives thereof, cellulose derivatives, biopolymers, and the like.
In many of the aforementioned subterranean treatments, surfactants also may be included in a treatment fluid, among other reasons, to impart certain surface active properties to the fluid. Such surfactants may be used as an emulsifying agent, a de-emulsifying agent, a foaming agent, a defoaming agent, a viscosifying agent, a dispersant, a wetting agent, and the like. Surfactants also may be used to enhance the removal of heavy oil from mineral surfaces in a subterranean formation and/or well bore.
In treatments where both viscosifying agents and surfactants are desired to treat the same portion of a subterranean formation or well bore, current methods generally involve pumping multiple additives into the formation, either in the same treatment fluid or in several different treatment fluids. However, if the desired surfactant is incompatible with the desired viscosifying agent and/or another additive, it may be difficult or impossible to pump these additives into the formation or the well bore at the same time. Pumping these different additives sequentially may increase the amount of time needed to treat the formation and/or complicate the design of the treatment process. Moreover, if a surfactant is pumped into a well too early, the concentration of the surfactant may decrease before the treatment can be completed (due to degradation, fluid loss, and/or other factors), resulting in ineffective or incomplete treatment.
While the present disclosure is susceptible to various modifications and alternative forms, specific example embodiments have been shown in the figures and are herein described in more detail. It should be understood, however, that the description of specific example embodiments is not intended to limit the invention to the particular forms disclosed. On the contrary, this disclosure is to cover all modifications and equivalents as illustrated, in part, by the appended claims.